Only a few substituted imidazo[1,2-a]pyrazines are known. The parent imidazo[1,2-a]pyrazine has been prepared only recently, in substantial yield (39.2%), by DePompei et al., J. Het. Chem. 12, 86 (1975).
Employing a modification of this procedure which condenses aminopyrazines with .alpha.-halo carbonyl compounds prepared in situ from their diethylacetals, and newly developed methods involving condensation between a dihalopyrazine and an .alpha.-hydroxy-alkylamine or a propargyl amine, a number of novel imidazo[1,2-a]pyrazines have been prepared and converted to piperazinyl-imidazo[1,2-a]pyrazines.
These compounds are found to be 5-hydroxytryptamine agonists or reuptake blockers, and accordingly show anorexic, antidepressant, antihypertensive and/or analgesic activity. They are also .beta.-blockers and are accordingly antiarrhythmic agents. In addition the compounds block the self-administration of nicotine in laboratory animals and are thus antismoking agents.
Therefore it is an object of this invention to provide novel piperazinylimidazo[1,2-a]pyrazines with anorexic, antidepressant, antihypertensive, analgesic, antiarrhythmic, and/or antismoking activities. It is also an object of this invention to provide procedures for preparing these novel compounds.
Another object is to provide pharmaceutical formulations for the administration of these novel compounds.
A further object is to provide a method of producing an anorexic, antidepressant, antihypertensive, analgesic, antiarrhythmic, and/or anti-smoking effect in a mammalian (human or animal) patient in need of such treatment.